The present invention relates to a programmable electronic calculator and, more particularly, to a portable, programmable electronic calculator or a portable, personal computer.
In such an electronic calculator, an optional program can be set in an electronic calculator through the use of a key input panel. More specifically, an operator typically introduces a desired program into an electronic calculator through the key input panel. The thus introduced program is stored in a semiconductor memory and the program is read out at a desired time to conduct the programmed operation. The semiconductor memory is associated with a backup battery so that the program stored in the semiconductor memory is not erased even when a main power supply is interrupted.
However, in the conventional programmable electronic calculator, there is a possibility that the program may be unintentionally changed or erased due to an erroneous operation conducted at the key input panel.
Accordingly, an object of the present invention is to provide a novel system in a programmable electronic calculator for preventing an unintentional change of an optional program.
Another object of the present invention is to provide a lock system in a programmable electronic calculator, which functions to preclude the programmable electronic calculator from being placed in a program mode.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
To achieve the above objects, pursuant to an embodiment of the present invention, an optional program is introduced into and stored in a read/write memory (random access memory) when a programmable electronic calculator is placed in a programming mode. The thus stored program is executed at a desired time when the programmable electronic calculator is placed in a run mode. The mode selection between the programming mode and the run mode is conducted through the use of a mode selection key. When a lock command is introduced into the programmable electronic calculator, the programmable electronic calculator is not placed in the programming mode even when the mode selection key is operated. That is, the programmable electronic calculator is not placed in the programming mode even when the mode selection key is erroneously operated while the programmable electronic calculator is in the run mode, thereby protecting the optional program stored in the read/write memory from being unintentionally changed or erased.